A typical discharge tube operates at a high frequency and at a high voltage. Typically, the power supply available is at a lower voltage than is necessary for the operation of the discharge tube, and consequently the voltage has to be "stepped-up" using an appropriate transformer. Leads extend from the transformer to the ends of the discharge tube, these leads carrying the high voltage, high frequency current. These leads are relatively expensive, since the leads have to be well insulated, because of high voltage carried by the leads, but also the leads may typically form a dipole, meaning that the leads radiate significant amounts of energy. This can cause interference in nearby electrical apparatus.